The invention relates to a passive automotive restraining system for protecting occupants of a vehicle during impact. A passive restraint is a device or system designed to provide for the reduction or elimination of injury to occupants of a motor vehicle without requiring any overt action on the part of the occupant. One method of passive protection is to design vehicle interiors (i.e., steering columns, dashboards, and windshields) that safely absorb as much energy as possible. Another method of passive protection is the use and implementation of passive seat belts and air bags. To meet performance requirements of the Federal Government, interior design changes have not provided adequate protection and it has been necessary to provide belts or air bags.
Passive belts automatically move into position when an occupant either first enters a vehicle or as he closes his door. The installation of passive belts was initiated to encourage higher rates of belt use. However, the passive belt system could be disabled in vehicles by simple mechanical means.
Air bag systems provide a passive approach for restraint in a vehicle which is less intrusive and more difficult to disable. Such systems are designed to deploy into position in about 25 milliseconds to protect either the driver or passenger. The current generation of air bags is usually made from a porous nylon material that is inflated by a pyrotechnic inflator that produces nitrogen gas. A driver's side bag is usually about 2.5 cubic feet in volume and is installed in the steering wheel hub. Passenger side bags are generally much larger and are installed in the dashboard in front of the right outboard seating position to protect the passenger. Both passenger and driver's side bags may be used along with knee bolsters to prevent submarining of the occupant and reduce femur loading. Air bags protect occupants substantially in frontal or near frontal crashes of up to speeds of 35 m.p.h. However, they do not offer substantial protection in rear end collisions and their effectiveness in side or angle impacts, or roll overs is questionable. As a result, air bags still require belt usage to achieve good performance in other than frontal crashes.
Air belts are another form of restraint that combine many of the aspects of seat belts and air bags. Air belts consist of an ordinary three point harness, in which the shoulder belt is inflatable. By inflating during an accident, the air belt tightly couples the occupant to the vehicle and spreads the restraining force over a larger area of the torso than does a traditional belt. As with regular seat belts, implementation of air belts require that the belt must be fastened before it has any value. Consequently, in comparison to air bags, air belts fall short in that they do not pose the advantage of being completely passive and non-intrusive.